The long-term objective of this proposal is to study the changes in microbial composition of dental plaque during its longitudinal development, and to determine principles which may govern these changes. This proposal seeks to study the microbial composition of dental plaques adjacent to early active lesions of destructive periodontal disease. Comparison of this microbiota with that found in inactive sites should reveal which species may contribute to the initiation of periodontal diseases. The microbiota of healthy sulci contains mainly gram positive species, whereas the microbiota of periodontal pockets contains mainly gram negative organisms. Examination of the microbiota when there is the earliest detectable attachment loss should indicate how the microbial population changes from that associated with health, to that associated with active destructive periodontal disease. Active sites will be reexamined after treatment when sites are in remission. Comparison of the microbiota of sites in remission to that detected previously could also aid in determining which species are associated with early active periodontal attachment loss. Attempts will be made to culture organisms which might be present in the tissue adjacent to the periodontal lesions and healthy sites. Such species could represent the pathogens of periodontal sites. Identification of organisms in periodontal samples can be time-consuming and difficult. Semi-automated techniques will reduce the time needed to identify well-recognized species. Methods will be developed to adapt these techniques to fastidious anaerobic microorganisms. Certain species of gram negative assacharolytic rods can be difficult to separate from each other phenotypically, although species are distinct using DNA/DNA hybridization experiments. Additional methods for strain characterization will be sought to help identification of such isolates. Previous cultural studies of adult periodontitis revealed organisms which could not be classified. The "fusiform" Bacteroides were numerically dominant in many sites, but difficult to grow in broth. Capnocytophaga strains have been isolated which do not fit existing species descriptions. This proposal aims to characterize and classify these organisms using DNA/DNA homology techniques.